Burning velocity correlation of methane/air turbulent premixed flames at high-pressure and high-temperature

Turbulent burning velocities for methane/air mixture at pressure ranging from atmospheric pressure to high pressure ≤ 1 MPa and mixture temperatures of 300 K and 573 K were measured, which covers the typical operating conditions of premixed-type gas-turbine combustors. Based on the contours of the mean progress variable c = 0.1 determined using OH-PLIF images, turbulent burning velocity was measured. The S_T/S_L was also greatly affected by pressure for preheated mixtures at 573 K. Bending tendency of S_T/S_L curves with u′S_L was seen regardless of pressure and mixture temperature and the R_λ region where the bending occurs corresponded well to the region where the smallest scale of flame wrinkling measured as a fractal inner cutoff approaches the characteristic flame instability scale and becomes almost constant. A power law of S_T/S_L with (P/P₀)(u′/S_L) was clearly seen when S_T was determined using c = 0.1 contours, and the exponent was close to 0.4, indicating the agreement with the previous results using the mean flame cone method and the significant pressure effects on turbulent burning velocity.